I heard some interesting things at a NICASHI meeting recently and thought I would pass it along.

There are flow restrictors so only the set water temp will leave the unit. If you set the water temp higher then there will be less water output.

THe flow ratings were setup with Ca. water temps and therefore in Chicago where winter water is 15 degrees colder you must derate the flow rating by about 40% to get accurate water GPM.

The newer tankless water heaters have replaceable parts/heat exchanger and life is 20 years or much longer if parts are replaced. Warr is ten years I think.

Home Depot sells the lowest quality and they will last 1/2 as long.

Service is needed to clean --I believe it is one of the sensors, from mineral buildup/scale. Or maybe it's the small filter screen.

If you turn the water off and on quickly then an unheated or cold water slug is sent down the line and may surprise someone in the shower...or something like that.

There are remote digital thermostats so temps can be changed. they recommend 108 degree output.

There's been much written about the relief valves. Rory James of Imperial Tankless says that Calif (where most are manufactured) requires them so they all have them so that they are standardized for all the US, even though the manufacturers say they aren't actually needed. (i hope you follow my explanation)

And as has been mentioned, gas line size may be an issue to get proper functioning and BTU's.

Quick thread drift. (sorry)

Hi Chris,

Where were you last night? Good program.
Same old dinner though.

Ok, back to topic!

__________________
Eric Barker
Moraine Woods Consulting, Inc.
Barrington, IL

hello eric,
I was planning to go but was too tired to fight the traffic. So i went to a block club meeting on a teardown / redevolopment in the neighbohood.

I've heard some talks from TrussJoist, what new tidbits did i miss?
take care.

For those not familiar with tankless units I finally got around to pulling together all of my various posts WRT my experience with these water heaters:

Paragon Home Inspection FAQ

Micheal,
Thank you very much for sharing what sounds like some hard learned information. Well done!

I am seeing more of these units, from some rather old cheap AquaStars (reconditioned models on eBay sell for $350) to the newer models. I really appreciate your comments about gas line sizing and improper installations. A lot of my inspections are rural properties built by "custom home builders" (stress the word custom), with little or no code inspections, many are on well water (which has many of its issues with water pressure and high mineral content), some on propane, and being in Montana we also have to contend with freezing temperatures. As a side note, one enterprising home owner replaced an old tankless gas boiler that supplied heat for hot water baseboard heat with a Rinnai on-demand water heater; seemed to work pretty well in a rather small house.

I have noticed sizeable fluctations in water temperture even on supposedly properly installed systems. Do you have any further information or thoughts about some of Chris's original comments? I've run into some info both of the below issues, but my info was pretty thin.


"There are flow restrictors so only the set water temp will leave the unit. If you set the water temp higher then there will be less water output.

And ---

"Service is needed to clean --I believe it is one of the sensors, from mineral buildup/scale. Or maybe it's the small filter screen."

Thanks again.

Terry,

On Takagi's, anyway, there is a inlet side screen which needs periodic cleaning:

see pp11 here: http://www.houseneeds.com/shop/manuals/tkd20manual.pdf

This is MUCH easier if you install a isolation valve set intended for tankless units:

Isolation valves from FAMOUS PLUMBING SUPPLY

Attached Images

Takagi-Filter.gif (44.7 KB, 11 views)

Check out Fine Homebuilding, Jan. 2008 issue. They have a section on this type of water heater and they address the two most common problems with them: 1) Cold water surprise effect and 2) Drooping-pressure effect. Suposedly adding a 10 gallon electric water heater and a big pump (Taco 006 for example) will solve both of these problems. It's a long explanation, if you can't find it I'll try to draw a diagram. Dave